Friday, April 30, 2010

Bending Over Backwards

One of my favorite science bedtime stories (didn't you have those when you were a kid? or now, if you're still one?) involves the French physicist Prosper-René Blondlot (1849-1930), whose principal claim to fame, sadly, was a non-discovery.

In this particular case, Blondlot was working in his laboratory in the wake of a flush of discoveries concerning radioactivity and X-rays. Apparently, he was trying to polarize X-rays (a tricky task owing to their high frequency and short wavelength), and as part of his attempt he placed a spark gap in front of an X-ray beam. After a few experiments with this set-up, it seemed to him that the spark was brighter when the beam was on than when it was off.

He attributed this to a new form of radiation, which he called N-rays after his home town and university of Nancy. He may have been influenced by all the work on radioactivity and X-rays then going on, but at any rate, he set about immediately to investigate attributes of the new radiation. It appeared, he said, to be emanated by many objects, including the human body. It was refracted by prisms made from various metals, although these had to be specially treated in order to prevent them from radiating N-rays themselves.

It was all very interesting, and for some time, there was a burst of scientific activity on N-rays. The problem was, the N-rays themselves were very shy and retiring, and many physicists had trouble reproducing the results obtained by Blondlot and his staff. But Blondlot always maintained either that they had inferior equipment, or inferior perception.

You see, there was no objective recording of N-rays. All one had was a subtle brightening of a spark, which Blondlot and his colleagues were already prepared to see. To lend at least some notion of objectivity to the research, Blondlot took photographs of the sparks and other N-ray phenomena, but this merely replaced subjective judgment of a live spark with subjective judgment of a photograph. Means for measuring the light output were not sufficiently reliable or accurate yet to resolve the matter.

What did resolve the matter in the end was a visit to Nancy by the American physicist Robert Wood (1868-1955). Wood had tried himself to detect N-rays and had failed signally. Frustrated at his wasted efforts, and curious as to the differences between Blondlot's staff and equipment and his own, he travelled across the ocean to see for himself.

Wood had by this time in his career established himself as something of a debunker, a sort of turn-of-the-century James Randi. But Blondlot was no charlatan; on the contrary, he was firmly convinced of his own discovery. So he had no misgivings about demonstrating his N-rays before Wood and others. He darkened the laboratory (the better to see the increase in brightness). He set his aluminum prism on a platform to refract the N-rays, made some measurements, rotated the platform a bit, made some more measurements, and so on, all the while casually detecting the N-rays. For his own part, Wood could see nothing of what Blondlot was describing. But he kept quiet, waiting for the experiments to conclude.

When they did, and the lights were turned back on, there was general astonishment, for despite all the careful measurements on the refraction of N-rays, there was no aluminum prism sitting on the platform. Wood had, it turned out, pocketed the prism early on in the experiment. The entire time, Blondlot and his staff had been obtaining gradually changing measurements of an unchanging experimental set-up. That spelled the end, for all intents and purposes, of N-rays.

What happened? Intentional deception can be ruled out rather easily, since Blondlot would have known that careful experimentation would eventually disprove N-rays; it would have been a most temporary fame. Nor was he a shoddy scientist. Before the N-ray affair, he was known for having measured both the speed of light and the speed of electricity through wires, a task that had stymied others, and which established that the two were very close (though not quite the same).

Consensus today is that Blondlot had simply wanted to believe in N-rays, expected and wanted to see the predicted brightening, so much that he really did see it, sincerely. It has been suggested that he may have been motivated by nationalism; X-rays were discovered by the German physicist Wilhelm Roentgen, and Germany had recently taken a sizable chunk of France, so that Nancy was now uncomfortably close to the French-German border. But my own feeling is that it almost doesn't matter. At some point, the desire to see his discovery of N-rays vindicated became its own driving force.

The N-ray affair is often cited in support of what is, in my opinion, a central—perhaps even the central—insight of scientific discovery: The easiest person to fool is yourself. And fooling yourself is a necessary prelude to fooling others; charlatanry would have been easier to expose. Exhibit A in support of this position is the sad fact that although N-rays essentially died a hard death in 1904, Blondlot lived on for another quarter century, continued to be productive in science, and took his belief in the existence of N-rays to his death.

It is because it is so easy to fool oneself that science is, and must be, an essentially social activity. It is often said that in science, experimental data rules the day. That's overstating it a bit. Experimental data is indeed necessary for science to progress, but that data means little without scientific theory to organize it (and vice versa). It's not that the data is more important than the theory, but that it validates it, makes it less likely to fool yourself or anyone else. And there's a strong social pressure, within the scientific community, for one to bend over backwards in an attempt to subject one's theories to as much scrutiny as possible. It's that intense examination, which eliminates many theories but marks the ones that survive with an imprimatur of robustness, that distinguishes science from so many other human activities (ahem, politics?) and has made it one of the most successful endeavors of all.

Wednesday, April 14, 2010

Back, Slash, Back!

Remember this post? Probably not, but now I have some company and/or vindication. Check out this xkcd comic, drawn by the redoubtable Randall Munroe.

Observe: Friends don't let friends say "backslash" in their URLs.